So when you drive on the border of the map in H7 k3/6/9 there is like a visual borderline between being out of combat or in the map. The clue being the different level of detail on terrain textures. And where those two types of textures meet, there is a small ditch, 1-3 meters deep, but just before that ditch is actually a invisible canyon that will trap you and your vehicle. See pictures.